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Adult male Bullock's Oriole.

A characteristic bird of open woodland in western North America—especially riparian woodlands with large cottonwoods (Populus spp.), sycamores (Platanusspp.), and willows (Salix spp.)—Bullock’s Oriole overwinters in western Mexico. In summer, this species eats mostly arthropods, readily augmenting its diet with ripe fruit. Older males have bright black and orange-yellow plumage and females have a generally grayer body with yellower head, breast, and tail; younger males resemble females, but have black on the throat.

Bullock’s Oriole hybridizes frequently with the Baltimore Oriole (Icterus galbula) in the Great Plains region at the eastern limit of its distribution, even though these 2 species differ markedly in appearance, behavior, molt cycles, and vocalizations, and somewhat in size. Because of this hybridization, these 2 species were at one time considered a single species, the Northern Oriole (I. galbula;
American Ornithologists' Union. 1983. Check-list of North American Birds, 6th ed. Washington, D.C: Am. Ornithol. Union.
American Ornithologists' Union 1983). Most of the interbreeding occurs in the Great Plains, however, even in areas where hybrids are frequent, many individuals are of the parental phenotypes. In addition, the width of the hybrid zone appears to be stable (
Rising, J. D. 1996c. The stability of the oriole hybrid zone in western Kansas. Condor no. 98:658-663.
Rising 1996c,
Carling, M. D., L. G. Serene and I. J. Lovette. 2011. Using historical DNA to characterize hybridization between Baltimore Orioles (Icterus galbula) and Bullocks Orioles (I. bullockii). Auk no. 128 (1):61-68.
Carling et al. 2011), and in 1995 the 2 were once again recognized as separate species (
American Ornithologists' Union. 1995. Fortieth supplement to the American Ornithologists' Union Check-list of North American Birds. Auk 112 (3):819-830.
American Ornithologists' Union 1995).

Bullock’s Oriole was described and named by William Swainson in 1827 on the basis of material collected by William Bullock and his son, also William. In his description, Swainson wrote, “This, the most beautiful of the group yet discovered in Mexico, will record the name of those ornithologists who have thrown so much light on the birds of that country” (
Mearns, B. C. and R. F. Mearns. 1992a. Audubon to Xántus: The lives of those commemorated in North American bird names. New York: Academic Press.
Mearns and Mearns 1992a: 555).